Chapter 6: Agronomical and Morphological Analysis in Control and
6.3 Nitrogen phosphorous and potassium
Total nitrogen, available phosphorous, and exchangeable potassium content were displayed in Figures 6.1 to 6.4. All the water samples used for research were subjected to trace nitrogen and potassium analysis to enhance wheat growth. As soil is an essential source through which elements such as nitrogen, phosphorous, and potassium may be transformed into the plant roots, it is necessary that the soil sample from the field was analyzed regularly before and after the treated wastewater to detect whether the composition of these elements is sufficient. In soil, plants are found to utilize nitrates. Since plants obtain their nitrogen from nitrates, other nitrogen forms' transformation is necessary for their plant growth. In soil solution, the standard is such that the presence of total nitrogen content more than 30 mg/L indicates an unacceptable and potential danger to the crop (Pano & Middlebrooks, 1982).
The prevailing compound in the highest concentration was nitrogen in Al Ain treated wastewater block with 355.33±3.83%. In contrast, the untreated control showed the highest nitrogen content, with 243.37±2.18% in the surface layer, compared to the safe limit (<5 mg/L). These values are higher than (<500 µg/100 mL) ideal requirements set by standard guidelines. While the highest percent of 348.35±0.83 was observed in Al Ain treated wastewater soil sample, the moderate value of 179.0±0.89 in control soil sample of the subsurface layer (30-60 cm depth) (Figure 6.4). It is also natural that there is a high % nitrogen in the surface layer because of the soil's regular irrigation water supply. Soil becomes decreased nitrogen % may also be because of the
presence of corresponding high absorption of nitrogen in the subsurface layer, which has given an idea of the possible absorption mechanism of roots in the supply of required essential nutrients. The experiment field area was found to have excellent total N% quantity.
The phosphorus content of the treated and control irrigation water samples was found to be higher than the food standard guidelines. A high proportion of the phosphorous element is considered a potential danger and involves eutrophication risk for the standing crops. In treated water, the standard is such that the presence of more than 10 mg L-1 of the phosphorous (1000 ug in 100 mL) is considered to be an indicator that the water is not acceptable (Metcalf & Eddy, 2003; Pescod, 1992).
Before water treatment, the mean average value of available phosphorous content of the test sample of T1V1, T1V2, T2V1, and T2V2 were 19.29±0.05, 17.30±0.08,19.32±0.03, and 17.33±0.02 ppm, respectively. Simultaneously, the control had a minimum of 7.92±0.03 ppm in T1V1 of the surface layer. While the highest value of available phosphorous (AVP) was observed with the concentration of 27.53±0.40 ppm in the treated T2V2 surface layer sample, the highest was 14.88±0.10 ppm in the treated T2V2 of the subsurface layer. The presence of less AVP content in the subsurface indicates high uptake of elements and development of roots. The phosphorous value was found to be much more compared to standard guidelines.
Application of treated water with less total solid phosphate (TSP) in fertilizer is desirable for crop health.
Potassium is responsible for enzyme activity and therefore provides considerable information about photosynthesis, peptide bond synthesis, physiological processes, development, and plant growth. The pigment carotenoid production in wheat
is dependent on potassium concentration. The presence of potassium >2.0 mg/L justifies that treated wastewater could promote maximum productivity. Stomatal opening and closure are due to potassium fluxes that occur during photosynthesis in the guard cells. Similarly, four trace elements have been identified as lesser in an amount from the treated wastewater. Potassium's presence of more than 30 mg L-1 in treated water (3000 µgm/100 mL) is considered unacceptable not fit for agriculture (Pescod, 1992; Ayers & Westcot, 1985). But, a significant amount of potassium available in the soil acts harmless.
The element potassium was present in excess concentrations (145.66±0.60 ppm) in (test sample T1V1 before treatment) followed by T2V2 (144.99±1.58 ppm equals 14400 µgm/100 mL) compared to FAO standards (200 µgm/100 mL). Because of the high potassium concentrations in treated water, it is unsafe to reuse it in agriculture (Unkovich et al., 2004). Excess concentrations of two essential elements, sodium and chlorine, can damage plants by reducing potassium absorption (Silberbush et al., 2005). The control sample had Ex K content ranges between 46.11±0.80 and 65.13±0.73 ppm in the surface layer (It shows 4600 µgm/100 mL). Compared to FAO standards (200 µgm/100 mL), the value is much higher, and hence the application of chemical fertilizer also was not required.
In comparison to the surface layer, the subsurface layer showed the highest Ex.
K concentration was observed in the treated T2V2 sample with the value of 117.43±1.05 ppm. The increased amount of Ex. K present in the field sample's surface layer and its comparison with the less amount of potassium in the sub-surface layer indicated the roots' absorption rate. Presumptive estimation of NPK, EC, and SAR using standard methods is essential. It has many advantages because the application of
chemical fertilizers to treated water is required or not can be justified generally. The trace metal profile of the water was compared with standard guidelines. It was found that these pH (above 7), Total N%, AVP (ppm) elements must be present high in the hydroponic solutions for crop production (Pais & Jones, 1997). The treated wastewater AD(T1), AA(T2), and control water samples were excellent overall quality.